Type 4 mechanical compression ratio, Why is the factory compression so low? Options

[jd74914]

If you're looking to improve thermodynamic efficiency, why are we talking about compression? Why are we talking about horsepower? Neither of things have any direct connection to head cooling.

That's not true. Theoretically otto cycle thermal efficiency is proportional to 1-(1/CR^0.4) or so.

Technically for best efficiency you want to optimize the temperature of the heads etc. to minimize heat transfer from the combustion process to the outside environment. From a thermal efficiency perspective, head cooling is considered a necessary loss (just like needed a TB is a pumping loss, etc.).

[jd74914]

I am modeling the Type 4 based upon other engines I have been involved with in the past.

What do you mean by modeling? The past experience kind or the computer/math kind (WAVE, GT-POWER).

[Bulldog9]

Eh, I'm not buying it.

Driveable? Porsche sold thousands of these cars making less than 100HP and were/are completely driveable and enjoyable. That's subjective anyhow.

All you've talked about is HP/liter and ridiculous compression ratios. Now you are looking to maximize thermodynamic efficiency?

You also seem to be ignoring the 'collective intellect'

I just finished a 2056 build (you can look at the #770 Update thread). I havent put on a dyno yet, but even in a 911 body, the car is responsive, has great driveability, power and loves to rev to redline. I'm guessing will be at the 125-130 HP range.

There are dozens of build threads all over the 914 world, aircooled.net, and if you've spent 5 minutes searching, you have found all the Raby stuff out there.

I'd like to see an example of one of these engines you've built.... or even what year your 914 is..... I think your talking in circles.... But hey, I'm just a grumpy guy. But I'm thinking TROLL ALERT here. Gonna be fun. (IMG:style_emoticons/default/popcorn[1].gif)

Thank you all for all your input. I knew that the collective intellect could be relied upon for valuable insight and experience

To answer a few comments/observations made, I am trying trying to maximize the thermodynamic efficiency of the design, not just max HP numbers...

Whatever the numbers end up being, it has to be drivable, have sufficient torque throughout the range and without going to endless amounts revs - I always try to minimize frictional losses.

this is not to be a track / race engine; just a daily driver

So to sum up, the enemy that needs to be addressed is heat management, and combustion chamber limitations, correct?

and yes, this sort of stuff always costs... its just a fun project - for an old guy.

I always welcome any and all comments / observations / experiences so keep 'em coming.

and to R Towle, do you have the camshaft specifications from your 13:1, 200 hp engine? I am specifically interested in your valve timing events

thanks again.

[Beebo Kanelle]

guys! I didn't mean to start a firestorm over this... I was just curious as to what the mechanical limitations of the type 4 engine was

no secrets here.

as for the concept, its a variation of the Atkinson / Miller cycle.

On circular intake ports it seems to be possible to minimize the pumping losses while taking advantage of a much greater expansion cycle. for example, instead of 1-2 pts, utilize 5-7 pts, allowing for a cooler exhaust and broadening the torque curve.

Years ago I took my Audi 5000 turbo and increased to CR to 11:8 +- while altering the cam timing events so the actual CR was 8:1 - that is my reference point - variations on this theme have been done to jaguar engines and a domestic v8 - all liquid cooled

I bought a 914 when I started having more time, and have become intrigued with the Type 4 engine.

as far as the modeling, right now its computer - and I'll see where that leads me.

[Mueller]

You really cannot model the Type IV using past motor builds, completely different designs...bore, stroke, combustion chamber, port shapes and flows.

What worked on your Chevy might not work here. I seriously doubt you are going to come up with magical engine recipe that hasn't been tried before.

[Beebo Kanelle]

probably not, it may all blow up - but I do want to look at it.

This is supposed to a fun exercise. and I think it will be.

[Beebo Kanelle]

and, if it all blows up, Y'all will be among the first to know

[Mark Henry]

guys! I didn't mean to start a firestorm over this... I was just curious as to what the mechanical limitations of the type 4 engine was

no secrets here.

as for the concept, its a variation of the Atkinson / Miller cycle.

On circular intake ports it seems to be possible to minimize the pumping losses while taking advantage of a much greater expansion cycle. for example, instead of 1-2 pts, utilize 5-7 pts, allowing for a cooler exhaust and broadening the torque curve.

Years ago I took my Audi 5000 turbo and increased to CR to 11:8 +- while altering the cam timing events so the actual CR was 8:1 - that is my reference point - variations on this theme have been done to jaguar engines and a domestic v8 - all liquid cooled

I bought a 914 when I started having more time, and have become intrigued with the Type 4 engine.

as far as the modeling, right now its computer - and I'll see where that leads me.

as for the concept, its a variation of the Atkinson / Miller cycle.

(IMG:style_emoticons/default/huh.gif) (IMG:style_emoticons/default/laugh.gif) (IMG:style_emoticons/default/lol-2.gif) (IMG:style_emoticons/default/av-943.gif)

The type 4 engine is a 50 year old 2 valve pushrod design based on a 85 year old 2 valve pushrod design. Add to this that the Type 4 has weak head sealing/bolt design for turbo or supercharging at anything but moderate levels.
The thing is unless you have made a amazing Type 4 flux capacitor breakthrough, what you are talking about would be better off started on a clean slate.

There has been all kinds of theoretical engine discussion here over the years. Not once has anything come to fruition that hasn't been already been firmly rooted in current or past technology.
Computer modeling can be great, but the Type 4 is oldschool, try building a couple of real T4 engines first. Then get back to us with some theories.

PM member veekry9, he would be a perfect muse, who knows maybe the two of you can make an amazing breakthrough. (IMG:style_emoticons/default/smile.gif)

[brant]

seriously.... as a hypothetical discussion you can get 100/hp per liter for a cost of 20K (and it will be necessary to pay someone to build it)

realistically.... you can not do it
yes some people can do it... they have years of experience and development

as a "new" 914 engine builder its not likely that you will get there
after 30 years and a million worth of development you will be able to
but realistically plan on 130hp from a 2.0 air cooled -4, and plan on a conversion if you want water cooled performance capabilities

[r_towle]

I would suggest you call around, talk with JAke Raby and the guys at FAT performance.
FInd a live customer near you that has a motor about 150HP or greater and ask them for first hand info, and possibly to take you for a ride.

You would be surprised what 150-180 HP will do in these 2500lb cars....

200hp in these cars means you need to be up to high in the RPM range to enjoy it, and have it be simple to drive. It also means a shorter lifespan than a 150hp motor...by a long shot.

Rich

[jd74914]

guys! I didn't mean to start a firestorm over this... I was just curious as to what the mechanical limitations of the type 4 engine was

no secrets here.

as for the concept, its a variation of the Atkinson / Miller cycle.

On circular intake ports it seems to be possible to minimize the pumping losses while taking advantage of a much greater expansion cycle. for example, instead of 1-2 pts, utilize 5-7 pts, allowing for a cooler exhaust and broadening the torque curve.

Years ago I took my Audi 5000 turbo and increased to CR to 11:8 +- while altering the cam timing events so the actual CR was 8:1 - that is my reference point - variations on this theme have been done to jaguar engines and a domestic v8 - all liquid cooled

I bought a 914 when I started having more time, and have become intrigued with the Type 4 engine.

as far as the modeling, right now its computer - and I'll see where that leads me.

Tough crowd. (IMG:style_emoticons/default/laugh.gif)

What software are you using? Commercial or homebrew? I saw your post looking for cam-to-lifter geometry so I assume you're at the connecting measured cam profile to actual lift stage.

It's be interesting to see what kind of efficiency gains you can see from increasing the expansion ratio. I do wonder what the trade off in terms of power will be with leaving the intake valve open so long. Either of these cycles offer relatively good efficiency gains (though a Miller might be tough just due to mechanical strength of the head attachment), but may fall down too much in the overall WOT power part since we don't have the variable valve timing knob to tune.

[HAM Inc]

If your goal is 100hp/liter T4 you're best chances are with a small bore, small displacement engine. The smaller the better.

[veekry9]

https://www.youtube.com/watch?v=zcPGfjUO3Yg


https://www.youtube.com/user/GrasshutPerformance/discussion
https://en.wikipedia.org/wiki/Julius_Mackerle
Turbo,efi,titanium weight-loss,auxiliary head and piston cooling,21st century sensors.
The heads lifting off will need a cure,like o-ringing them on to the nickies,stiffening the heads.
Note the use of modern off the shelf rods,as an economy.( Honda B16A H beam con rods)
Maximum effort calls for maximum control of heat in fine resolution.
An aluminum liquid coolant tube inserted into the head to sink heat will work too.
Not quite HD,but a bridgeport mill op,to keep a cool head.
The use of modern coatings to reduce friction and conduction is effective.
There,I spent some money for you,as any thing is possible.Methanol/Nitro fuel engine?
CadCam a set of new three valve heads you can graphite diecast for cheap and have a prototype shop do a short run on speculation.
I'll give you their number:
http://www.armstrongmold.com/pages/graphite_die_casting.html
(IMG:style_emoticons/default/happy11.gif)

/
Reading,it's good fer yuh.

Julius Mackerle: Air-Cooled Motor Engines, Cleaver-Hume Press, London 1961
Julius Mackerle: Air-Cooled Automobile Engines, The Institute of Mechanical Engineers, London 1961-2

[Mark Henry]

The 380hp corvair engine, with the coin in it you likely can do a /6 turbo engine

Turbo,efi,titanium weight-loss,auxiliary head and piston cooling,21st century sensors.
Well not what I'd call 21 century

The heads lifting off will need a cure,like o-ringing them on to the nickies,stiffening the heads.

The heads and sealing is't the big issue it's the two different lengths of the head studs. It's not O-rings it is fire rings, a solid steel ring precision matched machined into the head and cylinder. Old 911 turbo technology

Note the use of modern off the shelf rods,as an economy.
That's a given if using a stroked crank

Maximum effort calls for maximum control of heat in fine resolution.
An aluminum liquid coolant tube inserted into the head to sink heat will work too.
Not quite HD,but a bridgeport mill op,to keep a cool head.
The use of modern coatings to reduce friction and conduction is effective.
I use dry film, ceramic piston ton top coatings, etc.

There,I spent some money for you,as any thing is possible.Methanol/Nitro fuel engine?
Ok for a dragster...but street?

CadCam a set of new three valve heads you can graphite diecast for cheap and have a prototype shop do a short run on speculation.
I'll give you their number:
http://www.armstrongmold.com/pages/graphite_die_casting.html
(IMG:style_emoticons/default/happy11.gif)

I'm not trying to be a smart ass here, but there is nothing new or innovative in any of this stuff.

Now the last comment on three valve heads, we've been hearing about 4 valve per cylinder heads since the early 2000, we're still waiting....
But even they do get made my bet is they will be nothing but a novelty due to price.

[r_towle]

I admire what you are doing, and that you can do it.
Please share what you think might work because there are still some of us that may take a shot at it purely for fun

[Beebo Kanelle]

wow! Thanks to all for all the input.

to answer jd74914 questions: 1) initially, I just use a spiral notebook and a pen to gather info, 2) initial dynamic modeling using 'Dynomation", 3) take the data and build one... see how long it takes to blow up!

The #1 concern that pops up from the comments, after 'it can't be done', is the cylinder/head sealing - I can only assume that the Type 4 engine 'flops' around - and what about stability and flex of the crank?

That would necessitate small bore to minimize flex. But please tell me, is the head/cylinder just a registered fit under compression?

As far as air-cooling goes, does anything compare to Mr. Raby's DTM system used in conjunction with Nikasil?

Is there a book or source with all the torques, tolerances and dimensions? I know that after 40 years, there must be a lot of hard data, somewhere.

Thanks again

[r_towle]

Look at how the 911 turbo seals the head to cylinder.
Basically a small diameter wire machined into the head and cylinder, then crushed when torqued down.

[Mark Henry]

wow! Thanks to all for all the input.

to answer jd74914 questions: 1) initially, I just use a spiral notebook and a pen to gather info, 2) initial dynamic modeling using 'Dynomation", 3) take the data and build one... see how long it takes to blow up!


The #1 concern that pops up from the comments, after 'it can't be done', is the cylinder/head sealing - I can only assume that the Type 4 engine 'flops' around - and what about stability and flex of the crank?

Crank has two throws per main journal thus is has RPM limitations. You can't reduce rod journal size for different rod (ie rabbit rods) already been done, too much flex. Cylinder head bolt pattern is too big, upper studs shorter than lowers, fire rings have been tried, 5th head stud has been tried....

Never said "it can't be done", just said the T4 design has it's limitations and that conventionally in most cases it will have already been tried or done.
You have to keep in mind guys have been hopping these things up since the 70's and for the type 1 since the 50's.
Many also have proven track records , proven engine building creds and/or or proven products lines. We are talking real stuff not just theories.


That would necessitate small bore to minimize flex. But please tell me, is the head/cylinder just a registered fit under compression?
It sits in a bore

As far as air-cooling goes, does anything compare to Mr. Raby's DTM system used in conjunction with Nikasil?

In a 914 I still say the DTM is a waste of money, the exception would be a full race car with the shrouding cut away.
In VW beetles, T4 upright fan conversions the DTM is the snizzle.
I built a DTM/Joe Cali/Stock T1 hybrid shroud for my '67 bug, it came out great, but in retrospect the amount of time spent on it I wish I has just bought a DTM.
A DTM can be installed in a day.

Is there a book or source with all the torques, tolerances and dimensions? I know that after 40 years, there must be a lot of hard data, somewhere.

Bentley manual (IMG:style_emoticons/default/confused24.gif) Even performance most of that stuff is still the same as stock.
The stuff that changes for performance is mostly just dimensions.

Thanks again

[colingreene]

Is this thread still going? I lost interest in trying to help a while ago.

[Mark Henry]

Look at how the 911 turbo seals the head to cylinder.
Basically a small diameter wire machined into the head and cylinder, then crushed when torqued down.

No Rich, you don't understand what I mean by fire ring .
The Fire ring that is match machined into a high performance 911 turbo head and cylinder. The ring also stops cylinder head movement or shuffle.

(IMG:http://www.914world.com/bbs2/uploads_offsite/forums.pelicanparts.com-26-1455386123.1.jpg)

BTW I often work on a 500+hp porsche 911 turbo 3.8L high performance engine that has over 100hp/cyl.
The owner has well over $80K into the engine alone...this time around.